Lasers are presently employed for a wide variety of applications. For example, lasers are employed to process materials, such as by cutting, welding, heat treating, drilling, trimming and coating materials. Lasers are also employed to strip paint, remove coatings, clean surfaces and provide laser markings. Lasers can also be directly applied, such as via single mode optical fibers, for a variety of medical and other applications. Lasers are also increasingly employed in military applications, including laser weapon and laser ranging systems and sensor countermeasure systems. Laser communication systems have also been developed.
However, along with the ever-increasing number of applications in which lasers are used, the demands on the laser systems are also ever increasing. For example, a number of applications, including military and materials processing applications, are demanding lasers which emit increasingly higher power levels. In addition, a number of applications demand that the laser system produce an output beam which is of high quality, e.g., exhibiting predominantly or entirely fundamental or TEM.sub.00 mode characteristics. By being of high quality, the output beam can be more definitely focused to achieve higher brightness. As a result of the wide variety of applications in which lasers are used, the output beam may be required to be focused relatively near, such as within a few inches or a few feet as typically required by industrial applications such as cutting, machining, welding, drilling, paint stripping, or relatively far, such as at a distance of several kilometers as typically required in military applications such as laser weapon and sensor countermeasure systems.
Many laser systems have been developed to service one or more of the foregoing applications. For example, some conventional laser systems are scalable to produce an output beam having different power levels. Typically, these conventional laser systems rely upon the combination of various coherent laser beams in order to produce a coherent output beam with a high power level. Since these conventional laser systems produce a coherent output beam, these laser systems typically require sophisticated optical elements in order to properly combine and/or focus the coherent laser beams. See, for example, U.S. Pat. No. 5,694,408 to Eric H. Bott, et al, which issued on Dec. 2, 1997 and is assigned to McDonnell Douglas Corporation, the contents of which are incorporated in their entirety herein. As will be apparent, the cost of these laser systems is therefore disadvantageously large, at least for some applications, as a result of the costly optical elements. In addition, other conventional laser systems fail to produce an output beam that is of high quality and, as a result, may have difficulty focusing or otherwise shaping the output beam. Still further, other conventional laser systems which do not produce a coherent output beam suffer from other disadvantages, such as being incapable of being readily scaled to produce a wide range of output power levels or requiring the laser sources to be immediately adjacent to one another which limits the options available to the system designer.
While a variety of laser systems have been developed to service specific ones of the foregoing and other applications, a need still exists for a laser system which can service a wide variety of applications, such as by providing an output beam that is scalable to different power levels and that can be focused to a target location that is either relatively near or relatively far. In addition, a need also exists for a laser system that produces an output beam having high quality that can be focused or otherwise controlled without requiring sophisticated optical elements that would significantly increase the cost of the laser system.